Gordon et al. in U.S. Pat. No. 533,660 disclose a novel family of .beta.-lactam antibiotics. The preferred oral antibiotics disclosed by Gordon et al. comprise the .beta.-lactam nucleus biologically activated by a sulfate (-O-SO.sub.3.sup.63 M.sup..sym.) substituent attached to the nitrogen atom of the nucleus, and an acylamino substituent in the 3-position as shown in the formula ##STR2## One such compound having the formula ##STR3## that is, [3S(Z)]-2[[[1-(2-amino-4-thiazolyl)-2-[[2,2-dimethyl-4-oxo-1-(sulfooxy)-3- azetidinyl]-amino]-2-oxoethylidene]amino]oxy]acetic acid (M.sup..sym. =H.sup..sym.), is further described in a copending application Ser. No. 695,775, filed Jan. 28, 1985, now U.S. Pat. No. 4,638,061. In the copending application pharmaceutically acceptable salts of that specific monosulfactam, e.g. ammonium salts, alkali metal salts such as sodium and potassium salts, alkaline earth metal salts such as calcium and magnesium salts, and salts derived from organic bases such as dicyclohexylamine, benzathine, hydrabamine, and N-methyl-D-glucamine are disclosed. Many of these salts that are desirable as medicinal agents are generally amorphous in their structure.
While the above compounds are very useful in that they have good activity against gram-negative bacteria, additional stable compounds having an even broader range of antibacterial activity have been sought.